Gen IV Small-Block Build - Budget LS Buildup

As the number of GM's production Gen III/IV V-8s proliferates, there's been a corresponding explosion in the number and variety of engine parts released to the public. Generally, they are interchangeable, but there are significant differences, too. And while General Motors and GM Performance Parts have done an admirable job getting crate-engine versions of production motors to market, there's plenty of room for the enterprising engine builder to mix and match from GM's parts bins to build unique, powerful, and-believe it or not-value-driven combinations.

Of course, "value-driven" shouldn't be confused with "cheap," but in the realm of relativity, value can easily be assessed when judged against, say, the list price for an LS7 crate engine. For reference, the LS7 displaces 427 cubic inches (really, it's closer to 428, but who's counting ...) and is rated at 505 horsepower and 475 lb-ft of torque. It also runs about $13,000 over the counter from your friendly neighborhood dealership parts guy-who'll be even friendlier when you order one.

Closer to reality for most enthusiasts are the production-based crate engines, such as the aluminum-block LS2 and the iron-block 6.0-liter engines found in seemingly zillions of GM trucks. These typically run between $3,500 and $5,500, making them good values for those who want to simply drop it in and go.

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The used LQ4 donor motor was completely disassembled, inspected, and rebuilt. Here, after the crankshaft and main caps were reinstalled, the crankshaft gear is installed using a 2-inch length of pipe and a hammer.

The engine combination outlined in this story is based on the truck-based 6.0L (364 cubic inches) LQ4 bottom end with a set of new L92 cylinder heads and a four-barrel carburetor. The L92 heads have tremendous airflow for off-the-shelf parts and are a performance bargain from GM Performance Parts. The engine dyno-tested to the tune of 480 horsepower with GM's Hot Cam and a whopping 540 horsepower with the General's racing-derived Showroom Stock camshaft.

And the price for all this glory? About $4,300-that's LS7 power territory for about a third of the price. Yeah, it seems like a value to us, too, and it would have been even cheaper if we hadn't bought two camshafts.

The impetus for the engine came from Bob Cross, a Michigan-based enthusiast who is very familiar with all of GM's latest engine offerings. The engine was destined for a '51 Chevy truck project, and Bob enlisted the help of his nephew Steve Marsa and his friend Cliff Urmanic, who performed the assembly. Dyno testing was done independently at a Flint, Michigan-based performance shop.

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The LQ4 engine uses hypereutectic (cast) pistons that have proven to be very strong. They have a dished head that will enable pump gas-friendly compression when used with the L92 heads and their smaller combustion chambers.

Affordable, Easy-To-Build ComboBuilding Gen III and Gen IV (alias LS) engines is remarkably easy and time-efficient; only four socket sizes are required to disassemble the engine: 8mm, 10mm, 13mm, and 15mm. Most of the bolts are interchangeable, too, so there's no fumbling with different-size bolts. They also use "dry" gaskets (no liquid, RTV-type sealers), and with their crank-triggered ignition systems, setting engine timing is as easy as plugging in the ignition controller.

The starting point for our value-driven 6.0-liter engine was a used LQ4 engine purchased for only $350. Most of the rest of the parts used to build up the engine were sourced from the GM Performance Parts catalog.

The L92 aluminum cylinder heads were the big enablers of the engine's admirable dyno results. They're the same heads used currently on the 6.2-liter-powered Cadillac Escalade and GMC Yukon Denali, but they are similar to the heads used on the Corvette Z06's LS7 engine. The have huge runners, 2.165-inch/1.600-inch valves, and flow a whopping 310-320 cfm on the intake side at 0.600-inch lift on the top end. They list for $399 apiece-pretty cheap for such a high-flowing aluminum head, in our opinion.

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Gen IV Small-Block Build - Budget LS Buildup

The used LQ4 donor motor was completely disassembled, inspected, and rebuilt. Here, after the crankshaft and main caps were reinstalled, the crankshaft gear is installed using a 2-inch length of pipe and a hammer.

The LQ4 engine uses hypereutectic (cast) pistons that have proven to be very strong. They have a dished head that will enable pump gas-friendly compression when used with the L92 heads and their smaller combustion chambers.

Two camshafts would be tested in the engine: GM's Hot Cam and Showroom Stock cam. First up was the Hot Cam, which boasts 0.525-inch lift and 219/228 duration at 0.050-inch lift on a 112-degree centerline. The Showroom Stock cam's specs include 0.570-inch lift and 239/251 duration on a 106.5-degree centerline. The Showroom Stock cam requires valve relief notches in the pistons when used with the LQ4 rotating assembly.

Another one of the easy, time-saving attributes of building LS engines is the drop-it-in lifter trays.

Engine building tip: The L92 heads only work on engines with 4.00-inch-orlarger bores, so a stock L92 or aftermarket 4.065-inch head gasket must be used.

The L92 heads are derived from the Corvette Z06's LS7 engine. They're currently used on the Cadillac Escalade and GMC Yukon Denali. When installed, they're initially torqued to 22 lb-ft, then 76 degrees. A final pass of another 76 degrees is done using a torque angle finder.

Here, the front oil gallery plug is installed; it prevents oil loss from the main gallery. Care must be taken to prevent it from being installed too deep, or it will block oil from the oil pump.

Here's another LS-building tip: We ported the Mellings gerotor-type oil pump as shown to reduce cavitation and improve oil flow. With the heavy-duty spring, the engine had 95 pounds of pressure on the dyno, so we put the regular spring back in the pump when the Hot Cam was installed.

The new ported oil pump slipped into place and was torqued down to 18 lb-ft.

With the heads installed, it's easy to see the cavernous intake ports that can flow up to about 320 cfm into the 68cc chambers. Valves measure 2.165 inches and 1.600 inches. They'll support up to 600 horsepower with the right intake, compression ratio, and camshaft combo.

Small part, crucial role: This rear barbell oil deflector-installed with the O-ring toward the rear of the engine-is vitally important. Without it, oil will not flow properly through the oil filter.

Because the engine was designed to run below 6,800 rpm, stock pushrods were employed. Stock rocker arms were used, too. They can take up to 0.600-inch lift-within the range of even the Showroom Stock cam-as long as their correctly matched supporting components are used, too. The intake rocker arms are offset to clear the intake port.

The LS engines have coolant crossover passages between the heads, in the front and rear, to reduce air lock. We made snazzylooking crossover tubes from braided line, giving the engine a decidedly high-performance look.

These new raised-script valve covers from GM Performance Parts look great (we painted the script and Bow Tie red), but they'd lose some of their visual impact with breathers and ignition coil packs. We fixed that with some creative craftsmanship.

A special valley cover tray was made of aluminum and used to house the PCV valve in the rear and a conventional breather at the front. For the PCV valve, a hole was drilled in the tray and a baffle was welded to the bottom. Then the back of the intake was drilled and tapped for a 1.8-inch pipe; a short piece of bent 5.16-inch brake line and rubber hose completed the fabrication.

At the bottom of the engine, an F-car windage tray, oil pickup tube/screen, and oil pan were used. Here the windage tray and pickup tube are installed.

Here's the Camaro oil pan being cinched down as the engine assembly nears completion.

Dyno tests netted a 471-horsepower/417 lb-ft best with the Hot Cam, which got the nod as the perfect street cam. It has a great sound and delivers a wide, wide powerband. The Showroom Stock cam made a lot of power, but requires an optimized setup of compression, gears, and more to be civilized.

After testing the Hot Cam, the higherlift, longer-duration Showroom Stock camshaft was inserted and the engine retuned. With the new cam, the engine picked up approximately 35 horsepower, with peak power numbers at 506 horsepower and 437 lb-ft of torque.